Central venous catheters or central line catheters are commonly used to administer medications, fluids, nutrients, blood products, and the like to patients. The central line catheter comprises a section of tubing that is inserted into a vein, such as the jugular vein in the neck, the subclavian vein in the chest, or a large vein in the arm and is threaded through the vein until it reaches a desired location in the body, such as the heart or a major organ. The catheter can be left in place for a longer period of time, e.g. weeks or months, than standard intravenous catheters or IVs inserted near the surface of the skin.
A problem that is often encountered with central line catheters is the formation of clots or occlusions within the lumen or around the end of the tube. The clots can result from precipitation of solids from fluids in the catheter, thrombosis in or around the catheter, and fibrin formation on the catheter walls, among others.
Clots and occlusions are treated by periodically flushing the catheter with chemicals configured to dissolve the clot or occlusion. For example, tPA (Tissue plasminogen activator) or rtPA (recombinant tissue plasminogen activator), alteplase, and recombinant urokinase are often employed to dissolve thrombolytic clots and fibrins while solutions of varied pH are employed to dissolve clots formed from precipitates. These de-clotting agents are typically forced into the catheter, such as by applying fluid pressure via a syringe loaded with the de-clotting agent, to fill any available space within the catheter with the de-clotting agent. In some practices, a vacuum is drawn on the clotted catheter using an empty syringe to collapse the catheter tubing and thereby provide additional space within the catheter in which the de-clotting agent can be disposed. Once in the catheter, the de-clotting agent is allowed to mix with and diffuse into any fluids in the catheter and to dissolve the clots or occlusions over a period of time. The de-clotting agents can then be withdrawn from the catheter and replaced with desired medicinal fluids or allowed to infuse into the body along with the medicinal fluids provided via the catheter.
Current practices of forcing the de-clotting agents into the catheter can also cause medicinal fluids that are in the catheter to be forced into the body. This can result in an unwanted bolus of medicine being provided to a patient and potentially an overdose condition in the patient. Depending on the medication, the patient may become very ill or suffer other deleterious effects from such a bolus.